Before campus local area networks (LANs), some computers used point to point serial links (e.g., digital data communications message protocol (DDCMP)) to communicate and were directly connected. The campus LAN introduced in the early 1980s had computers connected to a common communication infrastructure (e.g., an Ethernet LAN). Some early implementations of Ethernet used a bus with fat coaxial cable and vampire taps to connect the computers. A collision based access method was used to send data on the bus. Ethernet repeaters were introduced to extend the reach of the communication bus. In the middle 1980s Ethernet bridges were introduced to connect and segment the traffic into zones, which could provide multiple simultaneous communications between different pairs of computers.